Silvia Pascoli

In a vast hall, a hundred tuning forks are set out. Each one is a pulsar — an ultra-dense stellar remnant spinning at a furious rate, sending out radio pulses more precisely than any clock. When a low-frequency sound wave sweeps through the hall, all the tuning forks start to go slightly out of tune at the same moment.

A giant tank of ultrapure water sits deep underground in Japan. Its walls are lined with thousands of light-sensitive sensors that catch faint flashes — the traces of ghostly particles passing through the water.